Socio-economic inequalities in mortality persist into old age in New Zealand : study of all 65 years plus, 2001-04

A number of studies have explored the relationship between socioeconomic status (SES) and mortality, although these have mostly been based on the working age population, despite the fact that the burden of mortality is highest in older people. Using Poisson regression on linked New Zealand census and mortality data (2001 to 2004, 1.3 million person years) with a comprehensive set of socioeconomic indicators (education, income, car access, housing tenure, neighourhood deprivation) we examined the association of socioeconomic characteristics and older adult mortality (65+ years) in New Zealand. We found that socioeconomic mortality gradients persist into old age. Substantial relative risks of mortality were observed for all socioeconomic factors, except housing tenure. Most relative risk associations decreased in strength with aging (e.g. most deprived compared to least deprived rate ratio for males reducing from 1.40 (95% CI 1.28 to 1.53) for 65-74 year olds to 1.13 (1.00 to 1.28) for 85+ year olds), except for income and education among women where the rate ratios changed little with increasing age. This suggests individual level measures of SES are more closely related to mortality in older women than older men. Comparing across genders, the only statistically significantly different association between men and women was for a weaker association for women for car access.